Lifting jack



jug? 29 '1924. 1,503,343

w. G. ARMSTRONG LIFTING JACK Filed Sept. 23, 1921 2 Sheets-Sheet l "July29 1924.

1,503,343 W. G. ARMSTRONG LIFTING JACK Filed Sept. 23, 1921 2Sheets-Sheet 2.

Patented July 29, 1924i 1,503,343 CF'ICE.

WALTER Gr. ABIYISTRONG, F BRIDGEPORT, CONNECTICUT, ASSIGNOR TO THEAMERI- CAN TUBE AND STAlVII-'ING COMPANY, OF BRTDGEPORT, CONNECTICUT, ACOR- PORATION OF CONNECTICUT.

LIFTING JACK.

the Severalyiewe pawl and I form cam surfaces on the rear edges of theside walls of the retaining pawl, which are engaged by the lower end ofthe lifting pawl, as it moves down, to force the retaining pawl towardthe rack.

Another feature of my invention con` sists in the manner in which Isecure the casing to the base. Laterally-extending feet on the lower endof the casing are rigidly secured to the base and there are also a pairof side plates which are rigidly secured to the sides of the casing andhave flanges rigidly secured to the base.

Another feature of my invention consists in a simplified connectionbetween the central part of the spring and the reversing lever.According to this feature, the central part of the spring is formed intoa rearwardly-extending shank, which is directly connected, pivotally, tothe reversing lever.

In Figs. l and 3, I have shown a ack construction embodying my improvedpawl and my improved supportfor the casing. 'This construction includesthe pressed metal casing, 10, which has a longitudinally-extendingchannel formed therein and the rearwardly-extending portions, r11,forming a housing for the operating mechanism. The lateral flanges, 12,at the lower end of the casing are welded to the base-plate, 13. Iprovide a pair of side-plates, 14, which are welded to the sides ofcasing, 10 and which have the feet, 16, welded to the base-plate.

' 'Ihese side-plates may be pressed inwardly,

at 15, to lie against the portions, 11, of the casing.

The channel-shaped rack, 17, is slidably mounted in the channel of thecasing and has a plurality of teeth, 18, struck out from its base. Ahead, 19, is mounted on the upper end of said rack. A reinforcing col`lar, 20, is mounted on the upper end of the casing and has a tongue, 21,which extends within the channel of the rack and prevents dust and dirtfrom entering the interior of the casing.

A retaining pawl is pivoted in the casing on the pin, 22. Since theretaining and lifting pawls are identical, we shall use the samereference numerals in describing them. Each of these pawls comprises theparallei, spaced side walls, 23, connected by a front wall, 24, thelatter having a slot, 25, formed centrally therein. IVherever, in thisspeciH lication and the claims, I refer to the front wall of eitherpawl, I mean that wall of the pawl which is nearest to the rack. Atongue, 2G, is struck laterally from the rear edge of one side wall andforms a sort or bridge extending between the rear edges of the sidewalls, 23, and keeping them spaced correctly. rI`his ear, 26, isperforated, at 27,

- to provide a bearing for one end of the spring. Cam surfaces, 28, areformed on the rear edges of the side walls for a purpose to be describedhereinafter.

The operating lever, 29, has its rear end formed into a socket, 30, toreceive the handle, 31. This lever is pivoted in the casing on the pin,32, and the forward end, 33, of the lever, which extends into thecasing, carries a pivot pin, 34, on which the lifting pawl is pivoted.The end, 33, of the lever extends between the side walls, 23, of thelifting pawl. The easing has a cam surface, 42, which cooperates withthe back of the lifting pawl, as will be set forth more fullyhereinafter.

A wire spring, 35, has its free ends extending through the perforations,27, of the lifting and retaining pawls, respectively, and bearingagainst the ears, 26, at said points. The spring, 35, is provided with acentral loop, 36, which is connected by a link, 37, with the reversinglever, 38. This lever, 38, is U-shaped and has one leg extending intothe casing and pivotally connected with the rear end of link, 37, andthe other leg extending along the outside of the casing and terminatingin the finger grip, 40. The reversing lever is pivoted in the casing onythe pin, 39. The outer leg of the reversing lever engages the stop lug,41, pressed out from the side wall of the portion, 11, of the casing.

The construction shown in Fig. 4 is identical with that just described,except for the formation of the spring and its connection with thereversing lever. In this modified construction, the spring, 43, has itscentral portion bent or twisted to form a rearwarally-extending shank,44, having an eye, 45, which receives the pin, 46, by which the shank,44, is pivotally connected to the inner leg of the reversing lever, 38.The free ends of spring, 43, work in the perforations, 27, of the pawls,just as in the form previously described. In this modification, link,37, is eliminated, thus reducing the number of parts in the jack.

From the description of the parts given above, the operation of myimproved lifting jack should be readily understood.

In Fig. 1, the parts are shown in the liftingposition so that, when thehandle, 31, is worked up and down, the rack, 17 will be raised to liftthe load engaged by head, 19. In this position, the center of spring`35, is nearer the rack than the ends, and the ends ofthe spring,engaging the pawls at the perforations, 27, force the pawls toward therack. As the handle, 31, is depressed, the lifting pawl is raisedcarrying the rack with it, while the retaining pawl rides over a toothof the rack and snaps into engagement with the next lower tooth. Whenthe handle, 31, is raised, the rack is held from dropping by theretaining pawl, while the lifting pawl moves down, riding over a tocthnffthe `rack land springing into Ae11- gagement with the next lowertooth. This operation is repeated at each stroke .of the handle. Whenit` is wished to lower the load, the :reversing lever, l38, :is shiftedto the position-shown in Fig. 3. This-shifts the center of the spring,3,5, so that it is further from the rack than the ends of the springsand, consequently, they tend to move the pawls-away from-the rack. rFhistendency `is ineective as long as there isa loadon `the pawl. In Fig. 3,the handle is lowered and thespring 35, has withdrawn the retaining pawlfrom the rack. -As the handle, 31, is raised, the lifting pawl islowered'and the load causes the rack to drop with saidpawl. Toward theend of the upstrolre of the handle, the lower end of the lifting pawlengages the cam surfaces, 28, O n-.the back ofthe retaining pawl andforces the latter inta-engagement with the rack, so that lthefdownwardmovement of the rack is halted and theload is shifted from thelifting pawl to the retaining pawl. When this takes place, the spring,35, withdraws the lifting pawl from engagement with the rack. Now, thehandle, 31, is depressed land the lifting pawl, which is clear of therack, moves upwardly. Toward the end of this movement, the back of thelifting pawl engages the cam surface, 42, of the casing and is forced byit into engagement with the rack so that, as its upward movementcontinues, it takes the load from the retaining pawl and spring, 35,withdraws the latter from engagement with the rack. This operation isrepeated at each stroke of the handle. The operation of the modifiedconstruction shown in Fig. 4 is the same.

The improved pawl which I have disclosed is capable of supporting a veryheavy load, because the front wall, 24, is almost exactly in line withthe line in which the load is transmitted from the tooth of the rack tothe pivot of the pawl. This load is applied longitudinally of the frontwall and thus the full strength of the metal is utilized. This is trueof both the lifting and retaining pawls. The slot, 25, in the case oftheY lifting pawl, permits the central portion of spring, 35, to workthrough it. This results in a very compact structure. The ear, 26, notonly provides a bearing for the end of spring, 35, but also insurescorrect spac- ,ing of the side walls, 23, so that they cannot movetoward each other and bind on the inner end, 33, of the operating lever.The side plates, 14, give a very strong connection between the casingand the base, 13. As I have already indicated, the modified form ofspring, 43, results in a simpler construction by eliminating link, 37.

I am aware that the construction described herein may be alteredconsiderably without departing from the spirit of my invention and,511,811.09, .I ,c.1aim :my invention broadlyeas indicated by theappended-claims.

Having thus described my,invention,`what I-claim as `'new-and desire tosecure by Letters Patent is k:1. .A ldevice vof the class describedcomprising a casing, a lifting rack slidably mounted therein, a leverpivoted inI said, casing, anda vhollow lifting :pawl carried by saidlever and engaging the teeth of said rack,-sai-d pawl -havinga frontVwall, side walls-and an ear projecting from one side wall toward theother and perforated to receive `an actuating spring. p

A2. A device of the classdescribed comprising a casing, a rack slidablymounted therein,an operating lever pivoted in said casing, a hollow:lifting pawl carried by said lever and engaging said rack, a hollowretainingA pawl pivoted in the casing and-engaging said rack, each ofsaid pawls having a front wall, side walls and-a portion projecting fromone side wall toward the other and provided with a hole, al springhaving its endsextendingthroughsaid holes, and means forshifting thecenter of. saidN spring from one side to the other ofa straight lineconnecting said holes.V

3. A device of the class described compris ing a casing, a rack slidablymounted therein, an operating lever pivoted in said casing, a hollowlifting pawl carried by said lever and engaging said rack, a hollowretaining pawl pivoted in the casing and engaging said rack, each ofsaid pawls having a front wall, side walls and a portion projecting fromone side wall toward the other and provided with a hole, a springprovided with a central loop and having its free ends engaging in .saidholes, and means engaginosaid central loop for shifting the centraportion of said spring.

4. A device of the class described comprising a casing, a rack slidablymounted therein, an operating lever pivoted in the casing, a hollowlifting pawl carried by said lever and engaging the rack, a hollowretaining pawl pivoted in the casing and engaging said rack, each ofsaid pawls having a front wall, side walls and a portion projecting fromone side wall toward the other and provided with a hole, a spring havingits ends engaging in said holes, and a reversing lever pivoted on thecasing and con? vnected to the central portion of the Spring.

5. A device of the class described comprising a casing, a rack slidablymounted therein, an operating lever pivoted in the casing, a hollowlifting pawl carried by the lever and engaging said rack, a hollowretaining pawl pivoted in the casing and engaging said rack, each ofsaid pawls having a front wall, side walls and a portion projecting fromone side wall toward the other and provided with a hole, the front wallof so i llO

the lifting pawl having a slot therein, a spring working in said slotand having its ends engaging in said holes, and a pivoted reversinglever' connected to the central portion of said spring. f

6. A device of the class described comprising a casing, a rack slidablymounted therein, an operating lever pivoted inthe casing, a hollowlifting pawl carried by said lever and engaging said rack, a hollowretaining pawl pivoted in the casing and engaging said rack, each ofsaid pawls having a front wall, side walls and a portion projecting fromone side wall and provided with a hole, the front wall of the liftingpawl having a slot therein, a spring having a central loop thereinworking in saidslot and having its ends engaging in said holes, a pvotedreversing lever,'and a link connecting said loop and the reversinglever.

T, In a lifting jack, in combination with a easing, a rack and anoperating lever, a pressed metal pawl carried by said lever andcomprising a front wall, spaced side walls and a portion projectingklaterally from the rear edge of one side wall toward the other sidewall and provided with a hole.

8, In a liftingjack, in combination With a easing, a rack and anoperating lever', a pressed metal pawl carried by said lever andcomprising a 'front wall, spaced side walls and an ear struck laterallyfrom the rear edge oi' one side wall and bridging the space between saidside walls, said ear being provided with a hole.

9. In a lifting jack, in combination with a casing, a rack, and anoperating lever, a pressed metal pawl carried by said lever andcomprising a front wall, spaced side walls and an ear extendinglaterally from the rear edge of one side wall and perforated, said irontlwall having a central slot therein.

l0. In a lifting jack, in combination with a casing, a rack and anoperating lever, a channelsshaped, pressed metal pawl carried by saidlever with the base of the channel presented .toward the rack, said pawlhaving a perforated ear projecting laterally from the rear edge of oneoi' the side walls thereof toward the other side wall, and apavvl-actu-y ating spring engaging in said perforated ear.

In testimony whereof, I alflx my signature.

WALTER e. ARMSTRONG.

